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differential equations
Posted:
Jul 28, 1996 11:23 PM


Hi, I am a research student of economics. I want to solve a system of differential equations with Mathematica.
I wrote the follwoing command based on the example given in p.698 of 'Mathematica: A system for doing mathematics by computer'  ks=0.380884;cs=0.0282254;ws=0.846308; k0=ks/10; cprimess=0.00778013/0.257126; wprimess=0.966347/0.257126;
NDSolve[ {c'[k]== If[k==ks,cprimess, (0.012+0.952757k/w[k]^.7+0.11938/w[k]^.6 +2.6603c[k]/w[k]^.10.635171w[k]) /(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6 +2.6603c[k]k/w[k]^.10.635171k*w[k]^.30.447674w[k]^.4) ], w'[k]== If[k==ks,wprimess, (1.1938w[k]^.4+6.65074c[k]w[k]^.91.58793w[k]^1.3) /(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6 +2.6603c[k]k/w[k]^.10.635171k*w[k]^.30.447674w[k]^.4) ], c[ks]==cs, w[ks]==ws}, {c,w},{k,ks,k0}] 
Then I got the error message saying: NDSolve::deql: True is not a valid equation or list of valid equations.
I was able to solve a single differential equation before, but do not know how to cope with my problem now.
I would like to get some comments.



